A method and a device for cleaning the rotor blades and the nozzle ring of the axial turbine of an exhaust gas turbocharger are known from DE 35 15 825 A1. The cleaning device comprises a plurality of water nozzles which are arranged on the gas intake casing of the axial turbine and reach into the flow passage, and water piping. With a defined degree of contamination of the axial turbine, a cleaning requirement is sensed via a measuring and evaluating unit. Accordingly, water is injected into the flow passage via the nozzles which are arranged upstream of the stator blades. The water droplets which result in the process are transported by the exhaust gas flow to the stator blades or rotor blades of the axial turbine and cleanse these of the adhering contaminants. During a relatively short cleaning interval, a large quantity of cleaning fluid (about 3 l/min of cleaning fluid per m3/s of exhaust gas) is fed into the flow in the process in order to achieve a cleaning which is as thorough as possible. With this cleaning method, the engine load must be reduced at an early stage and during the entire cleaning process on account of the large quantity of water. This is necessary in order to avoid an unacceptably large increase of the exhaust gas temperatures during the cleaning process. An excessive increase of the exhaust gas temperatures during the cleaning process leads to thermal overstressing of the exhaust gas turbines and of the internal combustion engine.
It is also known from the prior art that in the starting phase of injecting cold cleaning fluid in high quantity (cf. above) onto the hot stator blades of the nozzle ring and rotor blades of the turbine wheel, an additional thermoshock cleaning effect can be achieved.
Not only the stator blades of the nozzle ring and the rotor blades of the turbine wheel, but also the turbine casing components are thermally very heavily stressed during the thermoshock cleaning. Avoiding the formation of unacceptably high thermal stresses, or even cracks, in the corresponding components is constructionally very expensive, requires elaborate control of the cleaning, and as a result gives rise to high costs.